Satellite control systems require momentum to be transferred from the spacecraft body to rotating masses. This is generally accomplished through electrical cylindrical motors turning weighted wheels, one each axis of yaw, pitch, and roll. These are called “reaction wheels.” Typical satellite control systems include three (3) reaction wheels and associated control modules. Satellites are limited in size and total mass by the capabilities of the launch platforms available to deploy the satellites in space. As such, typical satellite control systems necessarily have a required amount of hardware and associated mass that takes away from the mass that can be dedicated to payload and other systems that are desirable on a satellite.
The volume and power required by available reaction wheel systems constrain the minimum size of a three-axis stabilized satellite system. Current reaction wheel system enable a minimum size of 10 cubic centimeters (see e.g., CubeSat) Additionally since a cylindrical motor requires bearings which wear out, redundant units may be required for satellite to be able to meet the necessary reliability and life expectancy.
There have been several papers and even a patent over the years describing the general concept of using a spherical motor to control a spacecraft. However, no practical device has ever been produced or developed. See, e.g., “Attitude Stabilization of Satellites by mean of the free reaction sphere” H. Schröpl 1964 translated from the German and made available from NASA in 1965; U.S. Pat. No. 4,611,863, entitled, “Magnetically Supported and Torqued Momentum Reaction Sphere,” William Isely, Issued Sep. 16, 1986, PCT Patent Application WO 2007/113666 A2 entitled “Reaction Sphere for Attitude Control;” and NASA SBIR Phase 1 Noqsi Aerospace, Ltd. “A Reaction Sphere for High Performance Attitude Control,” study completed Dec. 10, 2011, all of which are hereby incorporated by reference. None of these documents present a workable spherical motor solution. None of these documents adequately solves the problems presented by reaction wheel systems. All of these documents teach considerably different control theories than are presented below.
What is needed is a spherical motor system that is capable of overcoming the problems found in the prior art.